You specify that you are most interested in fast wide-angle lenses for landscapes and nightscapes... they simply do not exist as affordable options in legacy lenses, and "fast" is not necessary for landscapes: you want lenses that are sharp when stopped way down... something the kit lens is actually good at.

Depends on how fast and how wide. 24-48mm F2.5-F2.8 legacy lenses are fairly abundant and cheap.

The kit lens smacks right into a diffraction wall right at about F20, which is really stopped down. I don't understand why, but it goes up to F32. At that, it's not pretty.